This invention relates to the art of methods and apparatus for producing platelet rich plasma or a platelet concentrate. In particular, the invention relates to automated, highly efficient methods for separating platelets and plasma and for combining these in a selected proportion to provide platelet rich plasma or platelet concentrate of selected concentration.
Common methods for producing platelet rich plasma (PRP) involve a xe2x80x9cgentlexe2x80x9d centrifugation of whole blood. Platelet concentrate (PC) results from a second centrifugation of the PRP.
The platelets in platelet rich plasma PRP or platelet concentrate (PC) posses granules that contain growth factors (e.g., PDGF, TGF-xcex2, and others), which aid in accelerating angiogenesis (wound healing) and osteogenesis (bone growth). PRP/PC, when combined with thrombin, may also be used adjunctively to control bleeding (hemostasis), seal wounds, and as a vehicle for the delivery of drugs and/or biological agents. Further, the handling characteristics of certain organic materials, such as bone powder, can be greatly improved by combining them with PRP/PC, with or without the addition of thrombin. Such a combination also provides more secure placement of organic materials, for example, into an orthopedic defect. Some properties of PRP/PC and thrombin (e.g., hemostasis and wound sealing) are similar to those of fibrin glue, except that fibrin glue has a greater adhesive property because of its concentration of fibrinogen above baseline levels.
A typical method of producing PC involves subjecting whole blood collected in a blood bag system to centrifugation to separate PRP from red blood cells. Then, the PRP is expressed from the first bag to a second bag and again subjected to centrifugation, which results in a concentration (xe2x80x9cpellerxe2x80x9d) of platelets (PC) and a supernatant of platelet poor plasma (PPP). The majority of the PPP is expressed to a third bag, leaving the concentrated platelets and a small proportion of PPP behind in the second bag, which is used for re-suspending the concentrated platelets. This method, with a typical platelet recovery efficiency of only 45%, is too cumbersome for point-of-care use and, as a result, does not lend itself to point-of-care production of autologous blood products.
One automated system for the production of autologous fibrinogen from plasma is known from U.S. Pat. No. 5,707,331 (Wells). That patent teaches a system for automated processing of whole blood by centrifugation into a plasma component that is further processed by physiochemical precipitation and further centrifugation into a fibrinogen component. The fibrinogen is recovered and provides a fibrin sealant when combined with thrombin.
The ability to produce PRP/PC on demand from small amounts of whole blood would greatly facilitate clinical utility of PRP/PC, and availability of autologous PRP/PC would eliminate the need for homologous PRP/PC, which may carry the risk of transmitting human disease. Further, it is often desirable to provide PRP/PC of a selected concentration to achieve a particular therapeutic outcome. However, the known methods presently used for producing PRP/PC are time consuming, inefficient, and do not lend themselves to production from small amounts of whole blood.
Accordingly, it is an object of this invention to provide a method and apparatus for processing efficiently small volumes of whole blood into PRP or PC of any selected concentration on demand, at the point of care, and in the clinical setting.
In accordance with the invention, small amounts of PRP or PC are easily produced by an automated method preferably carried out by a centrifuge such as that shown in U.S. Pat. No. 5,707,331 (Wells). The centrifuge shown in the ""331 Wells patent receives a disposable container, or processing disposable (PD), having two chambers, and in the method of the present invention, whole blood is first placed in one chamber of the PD. The centrifuge is then operated to cause the red blood cells to sediment to the bottom of one chamber resulting in a supernatant of PRP. The centrifugation is stopped/reduced causing the PRP to drain to the second chamber, either by gravity or by centrifugal transfer.
PRP in the second chamber is then centrifuged a second time by restarting/accelerating the centrifuge. The centrifuge is then stopped, resulting in: (1) red blood cells in the one chamber, (2) platelets (PC) at the bottom of the second chamber, and (3) platelet poor plasma (PPP) as the supernatant in the second chamber. The foregoing operation of the centrifuge is preferably automated.
The operator may then produce PRP/PC of a desired concentration by obtaining a prescribed volume of the plasma supernatant and re-suspending the platelets.
In a preferred embodiment, the operator inserts a blunt cannula attached to a syringe into the second chamber and withdraws a desired volume of plasma, which leaves behind a known volume of plasma. A second blunt cannula attached to a syringe is then inserted into the second chamber where the remaining known volume of plasma is used to re-suspend and recover the PRP/PC having increased platelet concentration.
There may be other ways to recover the platelets and plasma. For example, after completion of the automated steps, the operator could decant plasma from the second chamber by tilting the disposable container to cause an amount of plasma to return to the first chamber, leaving the desired amount of plasma in the second chamber. The remaining plasma and the platelets would then be mixed and recovered.
In one example, a patient""s whole blood sample is obtained, containing a typical platelet count of 220xc3x97103/xcexcl. Based on a typical platelet recovery efficiency of 60% and processing a typical blood volume of 50 ml, re-suspending the PC in 5 ml of PPP will provide PRP with a platelet concentration of 1,320xc3x97103/xcexcl, a six-fold increase in the platelet concentration.